Earth boring apparatus



July 23,

Filed March 18, 1954 J. P. SELBERG ETAL EARTH BORING APPARATUS 4 Sheets-Sheet l INVENTOR5-' John, fjelbecg and @fo/uz Zldqy July 23, 1957 Filed March 18. i954 J. P. SELBERG ETAL- EARTH BORING APPARATUS 4 Sheets-Sheet 3 INVENTORS Mm P56158 m;

Jilly 1957 J. 1 SELBERG ET AL EARTH BORING APPARATUS 4 Sheets-Sheet 4 Filed March 18, 1954 and Invent? United States Patent EARTH BORING APPARATUS John P. Selherg, Los Angeles, and John J. Udry, Van Nuys, Calif assignors to Borg-=Warner Corporation, Chicago, Ill., a corporation of Illinois Application March 18, 1954, Serial No. 417,092

2 Claims. (Cl. 255-4) The present invention relates in general to earth bore drilling apparatus and more particularly to an earth boring drill of the type employing a vertically reciprocating drill rod and bit which vibrates at a frequency substantially equal to the resonant vibration frequency of the rod and bit.

More particularly, the present invention is intended to provide an auxiliary device adapted to be utilized in con junction with earth bore drilling apparatus of the general type disclosed in the patent to A. G. Bodine 2,554,005.

In earth boring apparatus of the type disclosed in the aforementioned Bodine patent, suitable vibration generating mechanism is utilized for generating sonic vibrations in the drill rod and bit in order to provide the necessary force to execute the drilling operation. In such drilling devices, the vibrating bit is maintained substantially in engagement with the bottom of the well hole and the earth formation immediately adjacent to the bit is shattered either due to vibrations imparted thereto by the bit itself or due to the percussive action of the bit on the formation. In a drill of this type the bit reciprocates or vibrates vertically at very nearly the resonant vibration frequency of the massive drill rod and bit and the ampli tude of the vibrations of the vibrating bit is of the order of three-sixteenths to approximately one-half inch.

As is customary in oil well drilling operations, a suitable mud fluid is pumped into the well hole, downwardly through the drill string and drill rod, with the mud fluid emerging from the bottom of the drill rod being forced out of the well hole upwardly around the drill rod and drill string and inside of the well hole. As the mud fluid rises in the well hole in this manner it takes with it the formation fragments or chips of the formation which have been broken up by the bit.

In order to efliciently utilize the energy which supplies the force for vibrating the drill rod and bit, it is necessary that the drill rod and bit be acoustically isolated from the supporting drill string and derrick. Otherwise, the energy supplied to the drill rod and bit for vibrating the same is dissipated in the form of acoustic vibrations or waves which travel to the surface through the drill string and derrick. As a practical matter, when the vibrating drill rod and bit are not substantially acoustically isolated from the supporting drill string, the vibrations travel up the drill string and proceed to set the derrick in vibration at frequences and amplitudes sufliciently high to shake loose any partially loosened parts thereof. As is apparent, if a bolt or other article is shaken loose from the top of the derrick and falls downwardly, there is a definite hazard to the persons operating the drilling mg.

The principal object of the present invention is therefore to provide a device for acoustically isolating an acoustically vibrating drill rod and bit from the supporting drill string and derrick.

A further object of the present invention-is to provide an acoustic isolator adapted for disposition between'an Patented July 23, 1957 2. acoustically vibrating drill rod and bit and the supporting drill string whereby the bit may be held against the earth formation at the bottom of the well hole by a substantially constant force under all practical operating conditions.

A further object of the present invention is to provide a lost motion connection between a sonically vibrating drill rod and bit and the supporting drill string therefor, to thereby enable the operator of the drilling rig to more easily contol the drilling operation by making it possible for the drill rod and bit to travel continuously downwardly as the earth formation is shattered at the bottom of the well hole without the operator having to continuously lower the supporting drill string. In this connection, the lost motion connection between the drill string and drill rod affords relative sliding movement of the order of twenty inches to two feet so that it is necessary for'the drilling rig operator to lower the supporting drill string only when the bit has penetrated the earth formation by approximately this amount. Of course, due to the type of formation being drilled, the speed of penetration of the bit will vary and, accordingly, the frequency with which the operator must incrementally lower the drill string will vary.

A further object of the present invention is to provide a lost motion connection between a drill rod and the supporting drill string which is effective to acoustically isolate the drill rod from the drill string at all'times.

A further object of the present invention is to provide an acoustic isolator between a drill rod and its supporting drill string comprising a keyed connection between the drill rod and drill string for causing them to rotate in unison and permitting them to have relative sliding movement and including a resilient coupling means between the drill rod and drill string for isolating the drill string from vibrations in the drill rod.

Another object of the present invention is to provide an acoustic isolator between a drill' string and a vibratory drill rod wherein one of the members is telescopically received within the other and each of the members is provided with an abutment affording lost motion therebetween for acoustically isolating the memberswhen the drill rod rests entirely on the earth formation at the bottom of the well hole, and there being a compression spring means disposed between the abutments on the members for effecting a resilient connection between the abutments when the drill rod has penetrated the earth suificiently deep to take up all of the free lost motion.

Briefly, the present invention contemplates providing a pin member at the upper end of the drill rod adapted to be telescopically received within a generally elongated cylindrical portion formed at the bottom end of the drill string. Suitable abutments are formed on each of the members which provide a lost motion connection between the drill rod and drill string and which lost motion connection is effective to acoustically isolate the drill rod from the drill string. Compression spring means are disposed between said abutments and have suificient strength to support the entire mass of the drill rod when it is hanging free without having the convolutions of the compression spring means engage each other. As a result, the drill rod is acoustically isolated from the drill string even when substantially the entire mass of the drill rod is supported by the drill string. The acoustic isolator provided by the present invention is particularly desirable in that it is simple and may be composed of rugged parts, the compression spring means being substantially the only part thereof which is subjected to great forces for any extended period of time.

Another object of the present invention is to provide an improved device for removing relatively coarse particles from a moving fluid having predominantly finer particles maintained in suspension therein.

A further object of the invention is to provide a device adapted to be disposed in the'path of movement of a moving fluid for deflecting the fluid from its normal course whereby relatively coarse particles in the fluid are directed so that they settle in a trap and are thus removed from the fluid.

Another object of the present invention is to provide an improved device for removing coarse abrasive sand particles from mud fluid as it is pumped down the drill string of an earth bore drilling apparatus and comprising a cap disposed on the leading end of a hollow drill rod shaft projecting concentrically into the lowermost end of said drill string, which cap is adapted to deflect the mud fluid radially outwardly from its flow path whereby the coarse particles settle into a trap formed between the shafts and the remaining mud fluid passes throughperipheral openings in the cap into the drill rod.

The present application is concerned chiefly with the features of the device in the acoustic isolator for removing coarse abrasive particles from the mud fluid and only these features have been claimed herein. The constructional details of the pilot bearing and lubricator and of the improved kelly, and the general features of the acoustic isolator have been disclosed and described in detail herein in order to provide a better and more thorough understanding of the present invention, however, each of these features has been made the special subject of other copending patent applications filed of even date herewith. The constructional details of the pilot bearing and lubricator are disclosed fully and claimed in the copending application of I. J. Udry, Ser. No. 417,157,

tion with the accompanying drawings, wherein:

Fig. 1 is a view showing a typical installation of an oil well drilling apparatus showing the surface equipment and the drill string extending down into the well hole, with the drill rod and bit not being shown in this Fig. 2 is a view showing the drill rod and bit of the type disclosed in the aforementioned Bodine patent disposed in a well hole with the bit resting on the bottom of the well hole;

Fig. 3 is a view similar to Fig. 2 but shows the drill rod and bit suspended by the drill string with the bit hanging free, the entire mass of the drill rod being supported by the drill string;

Figs. 4A, 4B and 4C, when assembled with Fig. 4A above and Fig. 40 below Fig. 4B, disclose on a somewhat enlarged scale, the acoustic isolator comprising the subject matter of the present invention;

Figs. 5A, 5B and 5C, each disclose fragmentary sectional views of portions of the acoustic isolator, Fig. 5A disclosing the pilot bearing and lubricator for the pilot bearing at the upper end of the isolator; Fig. 5B disclosing the lost motion connection between the drill string and drill rod with the compression spring means disposed between abutments respectively formed on the Fig. 6 discloses a section view of the slidable driving connection between the drill string and drill rod and is taken substantially along the line 6-6 in Fig. 5C and v looking in the direction of the arrows; and

Fig. 7 is an enlarged sectional view of the device. f

June 10, 1953.

V are set forth in said Currie et al. application.

4 removing coarse abrasive particles from the stream of mud fluid being pumped down the drill string, and showing the mud flow path.

Referring now to the drawings wherein like reference numerals have been used in the different views in order to identify identical parts and with particular reference to Fig. 1, the equipment disposed on the surface of the earth above the well hole will first be described. This equipment is conventional and includes derrick 10, draw works 11, driving rotary table 12, kelly 13 extending through table 12, swivel 14 coupled to the upper end of the fluid passage through kelly 13 and hook 15 supporting the hail of swivel 14. The hook 15 is suspended by means of a traveling block 16 and cable 17 extending from the top of the derrick 10 and the cable 17 is wound on the usual hoisting drum (not shown) of the draw works 11. Mud fluid, such as is conventionally employed in rotary oil well drilling operations, is pumped through a supply line 18 from a supply tank or sump 19 and is delivered under pressure by a pump 20 through a pipe 21 and hose 22 to the gooseneck of swivel 14, and from this point the mud fluid flows down through the kelly 13 and through a drill pipe string 23 coupled to the lower end of the kelly 13.

The kelly 13 and the drill string 23 extend into a bore hole 24 which extends downwardly into the earth. The bore hole 24 is lined for a suitable distance down from the ground surface by surface casing 25 which is supported by a landing flange 26 resting on a concrete footing 27 in the bottom of a pit 28. A blow-out preventer 29 is mounted at the head of the casing 25 and a riser 30 above the blowout preventer 29 is provided with a mud flow line 31. The mud flow line or delivery pipe 31 is shown as discharging to a conventional vibratory mud screen 32, and the mud is returned from the latter back to the sump 19 by means of a pipe line 33.

The drill pipe string 23 coupled at the lower end of the kelly 13 comprises a conventional drill pipe string and it will be understood that this drill string is made up of a number of usual drill pipe lengths coupled together by the usual tool joints (not shown).

The drill string 23 suspends a drill rod 34 in the well hole 24, the drill rod 34 being coupled to the drill string 23 by means of an acoustic isolator, indicated generally by reference numeral 35. Fastened to the drill rod 34,

at the upper end thereof is a turbine 36 and a vibration generator assembly or oscillator 37, both of which are of the type disclosed in the aforementioned patent to Bodine 2,554,005. It is not essential for a thorough understanding of the present invention to describe the turbine 36 and vibration generator assembly 37 in detail herein as the details of operation and construction of the turbine and vibrator are set forth in full in the aforementioned Bodine patent. It will suffice to state herein that the turbine 36 and vibrator 37 are capable of vibrating the drill rod 34 and a bit 38 secured at the lower end of the drill rod at a frequency approximately equal to the resonant vibration frequency of the drill rod and bit.

The drill rod 34, in addition to the turbine 36 and vibrator assembly 37 includes a massive elongated elastic longitudinally vibratory rod which is of substantial mass and length. This drill rod 34 may be made up of a plurality of steel drill collars, which are connected together preferably by means of tool joints of the prestressed type, such as is disclosed in the copending application of Udry et al., Ser. No. 394,432, filed November 25, 1953. It is contemplated that the lowermost drill collar of the drill rod 34 will be provided with an acoustic or sonic decoupler cell such as is disclosed in the copending application of Currie et al., Ser. No. 360,706, filed No further description of the decoupler cell will be given herein as the complete details thereof Immediately beneath the decoupler cell, the bit 38 is disposed and it is not considered necessaryfor a thorough understanding of the present invention to describe in detail the construction of the bit 38.

Referring now to Figs. 4A, 4B, 4C, 5A, 5B and SC in particular, the constructional details of the acoustic isolator comprising the subject matter of the present invention will now be described.

The drill string 23 has a lowermost drill collar 50which is coupled to an upper isolator sub 53 by means of a pre-stressed joint 54 of the type disclosed in the aforementioned Udry et al. application Ser. No. 394,432. The upper isolator sub 53 is coupled to a lower isolator sub 55 by means of a similar pre-stressed joint 56.

The upper end of the drill rod 34 comprises a hollow pilot sub 57 which has a substantially cylindrical outer periphery adapted to slide within a pair of lubricated bushings 58 and 59 in order to pilot the drill rod 34 within the lower end of the drill string 23. The hollow pilot sub 57 is rigidly coupled to a short adapter sub 60, these two subs being retained rigidly secured together by any desired means, such as welding indicated at 61. The short adapter sub 60 is coupled to a main internal isolator sub 62 by means of a joint indicated generally by reference numeral 63. The joint 63 includes mating tapered surfaces 64 and 65 respectively formed on the adapter sub 60 and on the isolator sub 62 and also includes mating threaded portions 66 and 67 respectively formed on the inner periphery of the lower end of the adapter 60 and on the outer periphery of the isolator sub 62. An O-ring 63a is disposed within a suitable peripheral groove formed in the interior surface of the adapter sub 60 and is effective to provide a seal between the adapter sub 60 and the internal isolator sub 62.

The joint 63 may also be pre-stressed by relatively turning the mating threaded portions 66 and 67 until the portions of the adapter sub 60 and isolator sub 62 between the threaded regions and tapered regions thereof are respectively pre-stressed in tension and compression. This is effective to insure that the joint 63 will remain tight while the drill rod 34 is vibrated by the vibration generator assembly 37.

The hollow isolator sub 62 is coupled to a hollow torque transfer sub 68 by means of a pro-stressed joint 69 of the type disclosed in the copending Udry et al. application Ser. N0. 394,432. The pro-stressed joint 69 is pinned by means of a pin on slug 70 in order to insure against this joint loosening as a result of vibrations induced in the drill rod 34 by means of the turbine 36 and vibration generator assembly 37. An O-ring 69a disposed in a suitable groove formed in the exterior periphery of torque transfer sub 68 provides a seal between the isolator sub 62 and the torque transfer sub 68.

It will be noted that the upper isolator sub 53 is quite thin for a considerable longitudinal distance and telescopically disposed within the upper isolator sub 53 is the thin internal isolator sub 62 of the drill rod 34. The radially spaced inner surface 71 of the sub 53 and outer surface '72 of the sub 62 provide an annuler cavity 73 for receiving compression spring means, indicated generally by reference numeral 74, therebetween.

The longitudinal extent of the annular cavity 73 .is defined by a pair of abutment stops comprising an upper abutment stop 75 having internal threads 76 adapted to be threaded onto the externally threaded portion 67 of the internal isolator sub 62 and a lower abutment stop 77 on the sub 55. The abutment stop 75 serves as a lock nut when it is screwed onto the threads 67 until it tightly abuts the lower end of the adapter sub 60. The lower end of the annular cavity 73 is defined by the abutment stop '77 which is received within the upper end of the lower ism lator sub '55. The abutment stop 77 .has a flange 78 adapted 'to seat upon the upper end of the lower isolator sub 55.

The compression spring means 74 disposed within the annular cavity 73 comprises a pair of compression springs 7.9 and80; having a stiff separating washer 81 disposed therebetween.

When the drill is disposed in the bore hole 24 and the bit 38 is disposed against the earth formation at the bottom of the hole, the relative positions of the drill rod 34 and drill string 23 are as shown in Fig. 2 of the drawings. In other words, so long as the drill bit 38 rests upon the formation at the bottom of the bore hole 24, there is considerable space in the annular cavity 73 above the compression spring means 74 and below the abutment stop 75. When the drill rod 34 hangs suspended in the bore hole 24, with the bit 38 held above the formation at the bottom of the bore hole, the entire mass of the drill rod 34 is suspended by the compression spring means 74. This latter condition is disclosed in Fig. 3 of the drawings. The compression spring means 74 are sufiiciently strong to support the entire mass of the drill rod 34, for so long as it hangs free, without causing the compression springs 79 and 80 to compress to the point where the successive convolutions therof rest upon each other. It is, therefore, apparent that under all conditions of operation the drill rod 34 is never rigidly coupled to the drill string 23 and thus it may be said that the drill string 23 is acoustically isolated from the vibratory massive drill rod 34.

In the operation of an earth boring drill of the general type disclosed therein, it has been found desirable to rotate the drilling bit as the boring operation progresses. This is due to the fact that when the bit 38 is not rotated as it is vibrated it tends to become locked in the formation at the bottom of the bore hole 24. The acoustic isolator 35 therefore includes means for transferring torque from the supporting rotary drill string 23 to the massive elongated drill rod 34. This torque transfer unit will now'be' dscribed. I

The torque transfer unit for coupling the drill string 23 for rotation in unison with the drill rod 34 is indicated gnerally by reference numeral 82. The torque transfer unit 82 comprises a sleeve 83 secured rigidly to the lower isolator sub 55 by any convenient means, such as welding for example, and provided with a plurality of semicylindrical openings 84 for snugly receiving an equal number of longitudinally extending pins 85. The converging sides 86 and 87 of each of the openings 84 serve to hold each of the pins in the openings 84. The openings 84 are so located in the sleeve 83 that the pins 85 each project inwardly beyond the inner periphery 38 of the sleeve 83.

A short abutment sub 89 is rigidly secured to the sleeve 83 by means of a plurality of screws 90 which extend through suitable openings in flanges 91 formed on the upper end of the abutment sub 89 and which extend into suitable threaded openings 92 formed in the sleeve 83. The flanges 91 on the upper end of the abutment sub 89 are also provided with a plurality of threaded apertures 93 for receiving suitable short set screws or locking screws 94 which may be turned until they reach the ends of the pins 35 for thereby holding the pins 85 in longitudinally fixed relation in the sleeve openings 84. The lower end of the abutment sub 89 comprises an annular fiat surface 95 adapted to abut an upper flat surface 96 formed on the upper end of the uppermost drill collar of the drill rod 34. The annular abutment sub 89 is adapted to rest upon the surface 96 of the drill rod-34 only when the entire mass of the drill string 23 is resting upon the formation at the bottom of the earth bore 24.

The torque transfer unit 82 also includes the hollow torque transfer sub '68 which is provided with a plurality of longitudinally extending grooves 97. A groove 97 is provided for each corresponding pin 85, with each of the grooves 97 comprising a-serni-cylindrical cavity formed in the torque transfer sub 68 and formed with a slightly greater radius of curvature than the radius ofcurvature vof the torque transfer pins 85. In the operadapted to rotate in a clockwise direction, as indicated in Fig; 6, and the pins 85 serve as keys, when seated within the openings 97, for transferring torque from the sleeve 83 to thehollow torque transfer sub 68. In order to minimize wear on the sides of the grooves 97, each of the grooves 97 in the hollow torque transfer sub 68 is provided with hard metal insert 98 made of some substantially wear-resistant material. Therefore, as the sleeve 83 turns in a clockwise direction, the pins 85 strike the wear-resistant inserts 98 and thus wear on the sides of the grooves 97 is held to a minimum.

Because of the fact that the grooves 97 are slightly larger than the pins 85, there is some freedom between the pins 85 and the defining walls of the grooves 97. This space provided by the freedom between the sides of the grooves and the pins 85 affords suitable passages for the passage of mud fluid between the grooves and pins, which mud fluid serves to cool these parts of the torque transfer unit which would otherwise heat up considerably due to friction between the pins 85 and inserts 98. The friction between the pins 85 and inserts 98 is considerable inasmuch as the drill rod 34 and hollow torque transfer sub 88 are vibrating at substantially the resonant vibration frequency of the drill rod 34 simultaneously with rotation of the torque transfer unit 82. Thus it is apparent that the friction between the pins 85 and the inserts 98 is of such a magnitude as to make it desirable to convey away the heat, generated by the friction, as rapidly as possible. It has been found that by providing the enlarged grooves 97, the mud fluid, which serves to provide the force or power for actuating the drill rod 34 and bit 38 as well as to provide the force for removing the chips of the formation which are broken away at the bottom of the earth bore by means of the bit 38, is also effective to cool the torque transfer unit.

Even though there is suflicient play of the pins 85 in the grooves 97 for mud fluid to pass through the grooves 97 in order to cool the torque transfer unit, the torque transfer unit 82 is effective in maintaining the drill rod 34 and drill string substantially concentric with respect to each other at the lower end of the acoustic isolator 35. Due to the rather extreme forces which act upon .the drill rod 34, it is essential that the uppermost end of the drill rod 34 also be maintained in concentric alignment within the lower end of the drill string 23. The means for maintaining the upper end of the drill rod 34 in concentric alignment with the drill string 23 will now be described.

The two bushings 58 and 59 comprise pilot bearings disposed between the inner periphery of the drill collar and the outer periphery of the hollow pilot sub 57. Both bushings 58 and 59 are designed so as to fit rather snugly within the inner surface 99 of the drill collar 50, but there is freedom for the isolator sub 57 to slide longitudinally or reciprocate within the inner peripheries 100 and 101 of the bushings 59 and 58 respectively.

The bushing 59 is held fixed with respect to the drill collar 50 by means of an inwardly projecting shoulder 102 formed on the inner periphery of the drill collar 50 and by means of an abutment or stop washer 103 disposed in a suitable groove formed on the inner periphery of the drill collar 50. Upward movement of the bushing 58 with respect to the drill collar 50 is limited by an abutment or stop washer 104 mounted in a suitable groove in the inner periphery of the drill collar 50, however the bushing 58 is free to move downwardly with respect to the drill collar 50. Each of the bushings 58 and 59 is provided with internal peripheral grooves 105. Radial openings 106 formed in each of the bushings 58 and 59 communicate with the peripheral grooves and a plurality of longitudinal passages 107 establish communication from an annular cavity 108, comprising the space between each of the bushings, to the internal peripheral grooves 105 formed in each of the bushings 58 and 59.

Each of the bushings 58 and 59 is respectively provided with a pair of O-rings 109 and 110, the O-rings 109 being provided for sealing the bushings 58 and 59 with respect to the drill collar 50 and the O-rings 110 being eflective to provide a seal between the inner peripheries of the bushings 58 and 59 and the outer periphery of the hollow pilot sub 57. The drill collar 50 is provided with a radially extending opening 111 for facilitating filling the cavity 108 with a suitable heavy lubricant or grease. A valve 112 provided at the outer end of the radial opening 111 is adapted to open when lubricant is to be forced into the cavity 108 and to automatically close so as to prevent the escape of lubricant from the cavity 108 through the opening 111. The bushing 58 is provided with a longitudinally extending passageway 113 having a check valve 114 provided at the inner end thereof, which check valve is adapted to open in the direction of fluid escape from the cavity 108.

When the cavity 108 is being filled with fluid lubricant or grease it is forced under pressure into the cavity through the valve 112. Air from within the cavity 108 is free to escape through the passageway 113 and through the check valve 114,. Since it is contemplated that the fluid lubricant admitted into the cavity 108 through the valve 112 will be rather heavy, such as a grease, for example, it will be readily apparent when the cavity becomes filled due to the escape of the fluid lubricant through the passageway 113. Due to the fact that the escape passageway 113 is small and since the bushing 58 fits quite snugly within the inner periphery 99 of the drill collar 50 and due to the further fact that the fluid lubricant admitted into the cavity 108 is heavy, the bushing 58 will tend to remain in the position shown in Fig. 5A and the cavity 108 will remain filled. When the acoustic isolator 35 is lowered into the earth bore hole 24 and mud fluid is pumped downwardly through the drill string 23 and drill rod 34, the pressure of the mud fluid is exerted on the upper end of the bushing 58 and on the check valve 114. The mud fluid pressure thus closes the check valve 114 and the bushing 58 tends to be compressed toward the bushing 59 so as to place the fluid lubricant within the cavity 108 under pressure substantially equal to the pressure of the mud fluid. Subsequently, as the pressure of the mud fluid varies, it will exert a corresponding variable pressure on the upper end of the bushing 58 so that the pressure of the fluid lubricant within the cavity 108 at all times remains substantially equal to the pressure of the mud fluid acting on the bushing 58.

The fluid lubricant in the cavity 108 communicates with the internal bushing surfaces 101 and 100, in order to maintain the outer surface of the pilot sub 57 lubricated, through the passageways 107 and 106 leading to the internal peripheral grooves 105. The O-ring seals 109 and 110 substantially seal the cavity 108 and since the pressure of the mud fluid outside of the cavity on the end of the bushings 58 and 59 is substantially the same as the pressure of the fluid lubricant, there is little tendency for there to be any escape of the fluid lubricant through or around the O-ring seals 109 and 110.

In order to insure against having large fragments of abrasive material reaching the mud turbine 36, means are provided in the acoustic isolator 35 for removing such large fragments from the stream of mud fluid and this means will now be described. At the upper end of the hollow pilot sub 57 a cap 115 is provided. The cap 115 is secured to the end of the pilot sub 57 by any well known or desired means, such as welding for example,

and the cap is adapted to be disposed in substantial concentric relation within the lowermost sub 116 of the drill string 23. The cap 115 is provided with a semi-spherical leading end 117 for deflecting the mud fluid outwardly toward the inner periphery of the sub 116. The cap 115 is also provided with a plurality of elongated slots ex- 1 tending longitudinally with respect to the cap 115, the

elongated slots in the cap 115 having been designated by reference numeral 118. The hollow pilot sub 57 is disposed in substantial concentric relation within the lower end of the drillstring sub 116 and an annular cavity 119 exists between the sub 116 and pilot sub 57. This annular cavity 119 extends from the lower end of the cap 115 downwardly to very near the end of the sub 116 where the inner periphery of the sub 116 is necked in, as indicated at 120. There is suflicient freedom between the necked-in portion 120 of the sub 116 and the outer periphery of the pilot sub 57 so that the mud fluid entering the cavity 119 may communicate with the upper end of the bushing 58-. It will thus be seen that full mud pressure is applied to the upper end of the bushing 58 so as to cause this bushing to act like a piston against the lubricant disposed in the lubricant cavity 108.

Mud fluid passing downwardly through the drill string 23, for the purpose of driving the turbine 36 and carrying away chips of the formation broken away from the bottom of the bore 24 by the action of the bit 3'8, passes downwardly through the lowermost drill collar 116 of the drill string 23 and upon reaching the cap 115 is deflected by means of the semi-spherical leading end'11'7 of the cap 115 toward the shell of the sub 116. In order for the mud fluid to proceed downwardly through the drill rod 34 it must pass through the openings 118 in the cap 115. The mud fluid flowing downwardly through the drill string 23 is represented schematically by the heavy flow arrow 124 When the mud fluid reaches the leading end 117 of the cap 115 closing the end of the pipe or sub 57-, the mud is deflected, as indicated at 125, toward the inner periphery of the sub 116. In order for the mud fluid to proceed downwardly through the pilot sub 57 it must pass through the openings 118 in the cap 115 and thus the direction of mud fluid flow is again changed, as indicated at 126, as it passes into the pilot sub 57. The openings 118 are limited in size and, of course, large fra'gment's 127 in the mud stream which have a greater dimension than the width of the slots 118 are strained out of the mud fluid and permitted to settle into the cavity or trap 119. The relatively smaller heavy coarse particles 127 tend to resist the "changes in the direction of movements thereof and instead of making the turn, as indicated at 126, these particles, being heavier than most of the mud particles which are maintained in suspension in the mud stream, settle into the mud fluid in the trap 119 and are thus prevented from reaching the turbine 36.

In order to facilitate removing the mud fluid and the settled coarse fragments 127 from the cavity or trap 1 19, a pair of plugs 121, which may be removed, are provided. The mud fluid may then be washed out through the holes provided when the plugs 121 are removed.

In order to permit and insure the free longitudinal vibratory and reciprocatory movement of the drill rod 34, the isolator subs 53 and 55 are each provided with a plurality of "radial openings 122. During downward {movements at the drill rod 34 the volume of the annular cavity 74 increases and by permitting the mud fluid from outside of the "isolator sub 53 to enter the cavity 74 there is no tendency for there to be a vacuum created within the cavity 74 as the drill rod 34 moves downwardly. Likewise, when the drill rod 34 moves upwardly relative to the two isolator subs 53 and 55, the volume of the cavity 74 decreases and the radially extending openings 122 permit mud fluid within the cavity 74 to escape to the outside of the drill string through the openings 122. There is thus no tendency for there to be any hydraulic lock created between the drill rod 34 and the drill string. The openings 122 in the lower isolator sub 55 also facilitate the passage of mud fluid into and out of the space between the lower isolator sub 55 and the hollow torque transfer sub 68. It will be recalled that it is desirable that some mud fluid pass between the pins 85 and the peripheries of the grooves 97 in the torque trans-fer unit 82 in order to provide cooling of the pins and metal inserts 98. Themud fluid, as stated previously, may pass downwardly through the grooves 97 and thereafter may escape to the outside of the drill rod by passing between the inner periphery of the abutment sub 89 and the outer periphery of the torque transfer sub 68 and thence outwardly between the abutment surfaces 96 and 95.

In the operation of the drilling apparatus of the type disclosed herein, the drill string 23 and suspended drill rod 34 are gradually lowered into the earth bore 24 until the bit 38 strikes the bottom of the bore 24. While the drill string 23 and drill rod 34 are being lowered into the earth bore 24, the relative positions of the drill string 23 and drill rod 34 are as disclosed in Fig. 3, with the entire mass of the drill rod 34 being supported by the compression spring means 74. The drilling rig operator will permit the drill string 23 to descend until the bit 38 strikes the formation at the bottom of the bore hole 24 and will permit the drill string 23 to descend thereafter until the abutment surfaces 94 and 96 are almost in engagement. At this time there will be some twenty to twenty-*four inches existing between the top of the upper compression spring 79 and the bottom of the abutment stop 75.

The actual drilling operation is then commenced. Mud fluid is pumped by the pump 20 downwardly through the drill string 23 in order to drive the turbine 36. The turbine 36 actuates the oscillator 37 and the drill rod 34 is thus set into longitudinal vibration. The vibration of the drill rod 34 is at substantially the resonant vibration frequency thereof. The bit then commences to break up the formation at the bottom of the bore hole 24 and the drill rod 34 descends, the abutment stop 75 moving downwardly at this time toward compression spring 79. The drilling rig operator will permit the drill rod '34 to descend relative to the drill string 23 for a distance of the order of approximately one and one-half feet. Throughout this entire peneration of the "bit 38 into the formation, the vibrating drill rod 34 is acoustically isolated from the supporting drill string 23 since the abutment stop 75 at no time even engages the spring 79 due to the fact that the entire mass of the drill rod 34 is resting on the bottom of the formation in the bore hole 24.

The drilling rig operator will then permit the drill string 23 to descend approximately one and one-half feet until the stops 95 and 96 are just free of one another. The entire procedure is then repeated. It will, therefore, be apparent that the work of the drilling rig operator is greatly facilitated as a result of the fact that he does not have to maintain a continuous watch on the descent of the drill string 23. In other words, the drilling rig operator may permit the drill string 23 to descend about one and one-half feet every half minute to one and onehalf minutes depending upon the rate of penetration of the" drill into the earth.

i If the drilling bit 38 penetrates the formation very rapidly, so that the relative positions of the drilling rod 34 and drill string 23 are like that disclosed in Fig. 3 the entire mass of the drilling rod 34 will be supported by the drill string 23 through the medium of the compression spring means 24. Assuming that the mud fluid continues to be pumped downwardly through the drill string so that the turbine 36 is continually operated, the massive drill rod 34 will continue to vibrate. The compression spring means 74 between the abutment stops 75 and 77 is effective to isolate the drill string 23 from the drill rod 34, even though the entire mass of the drill rod 34 is supported by the compression spring means 74. As a result, vibrations in the drill rod 34 are not transmitted to the drilling string 23 and derrick 10 even when the mass of the drill rod 34 is entirely carried by the drill string 23.

It is, therefore, apparent that the present invention provides an eflicient acoustic isolator between the telescopically arranged outer supporting drill string sleeve shaft and inner vibratory drill rod sleeve shaft of an earth bore drilling apparatus and by also providing the elongated cavity 73 affording lost motion between the stops 75 and 77 the work of the drilling rig operator is facilitated inasmuch as he does not have to maintain such a diligent watch on the penetration rate of the drill bit 38. By providing the unique kelly or torque transfer apparatus S2, rotation of the drill string 23 is readily transmitted to the drill rod 34 and wear of the different parts is held to a minimum. The unique piloting means for the telescoping drill string and drill rod sleeve shafts comprising the sleeve bushings 58 and 59 is very important since it is essential that the drill rod be maintained in concentric alignment with the drill string. Further, the means for lubricating the bearing surfaces of the pilot bearing is considered to be unique.

The cap 115 for deflecting the mud fluid to thereby facilitate settling of the coarse abrasive fragments 127 in the mud fluid into the cavity or trap 119 is also an important and desirable feature of the present invention.

The location of the torque transfer unit 82 below the acoustic isolating compression spring means 74 is considered to be very beneficial. By locating the torque transfer unit at a point below the isolating springs, it is therefore possible to utilize a pilot sub of small diameter and cross section and to utilize isolator subs of small cross section since they do not transfer torque loads. The pilot sub and all of the sections extending therefrom up to the cap 115 are subjected, in the main, only to tension loads and in designing these portions of the drill it is not necessary to consider torsion fatigue. Since the pilot sub need be of only a small diameter the problem of finding space for locating the isolator compression springs 74 is obviously simplified.

Another advantage of the present acoustic isolator arises from the fact that the isolating compression spring means is disposed between the torque transfer unit and the pilot bearing. It is thus possible to provide the greatest possible length between the pilot bearing and the torque transfer unit and this increases the stability of the internal isolator sub 62.

Another advantage afforded by the present acoustic isolator results from the fact that the outer isolator housing is composed of an upper and a lower isolator sub so that it is not necessary to handle a long heavy sub when the apparatus is being transported. Further, by providing the internal isolator sub 62 separate from the internal hollow torque transfer sub 68, case of handling is also facilitated and further, it is only necessary that the pilot sub be made of the highest quality steel having good bearing qualities. The use of the coil type compression springs renders the isolating unit practically fool-proof and maintenance is reduced to a minimum. Due to the fact that the compression spring means 74 are actually in operation only a very small percentage of the time that the drilling is actually taking place, the life of the isolating springs 74 is greatly increased.

From the foregoing description of the present invention it will be apparent that it provides an acoustic isolator adapted for use in an earth bore drilling apparatus having 'a longitudinally vibratory drill rod, which acoustic isolator is simple and effective and requires a minimum of effort in order to maintain the same in proper Working order.

It is contemplated that numerous changes and modifications may be made in the present invention without departing from the spirit or scope thereof.

What is claimed is:

1. In earth bore drilling apparatus employing a hollow drill string for suspending a massive elongated hollow vibratory drill rod wherein mud fluid is pumped downwardly through the drill string for driving a vibration generator which actuates said drill rod, means for removing relatively coarse abrasive particles from the mud fluid and comprising a pipe section at the upper end of the drillrcd and projecting upwardly into the lower end of said drill string, said upwardly projecting drill rod pipe section and the lower end of said drill string together including spaced portions defining an elongated annular trap concentrically disposed therebetween, an elongated cap having a dome-shaped top secured at the upper end of said drill rod pipe section, and means in said cap providing elongated mud fluid passages, said cap being effective to deflect the mud fluid radially outwardly as it flows downwardly to thereby cause the coarse particles therein to settle into said trap and said elongated mud fluid passages being effective to permit the remainder of the mud fluid to pass through the cap into said drill rod.

2. In earth bore drilling apparatus employing a hollow drill string for suspending a massive elongated hollow vibratory drill rod wherein mud fluid is pumped downwardly through the drill string for driving a vibration generator which actuates-said drill rod, means for removing relatively coarse abrasive particles from the mud fluid and comprising a pipe section at the upper end of the drill rod and projecting upwardly into the lower end of said drill string, said upwardly projecting drill rod pipe section and the lower end of said drill string together including spaced portions defining an elongated vertically extending annular trap concentrically disposed therebetween, an elongated cap having a dome-shaped top secured to the upper end of said drill rod pipe section, and means in said cap providing elongated mud fluid passages, said dome-shaped top being effective to deflect the mud fluid radially outwardly as it flows downwardly to thereby cause the coarse particles therein to settle into said trap and said elongated mud fluid passages being effective to permit the remainder of the mud fluid to pass through the cap into said drill rod, and means defining cleanout openings in said drill string at the lower end of said trap for facilitating removal of the coarse particles which settle into said trap.

References Cited in the file of this patent UNITED STATES PATENTS 1,084,978 Sullivan Ian. 20, 1914 1,463,006 Dardani July 24, 1923 2,554,005 Bodine May 22, 1951 2,628,819 Parsons Feb. 17, 1953 

